Lift steering systems and methods

ABSTRACT

A steering system includes a first wheel and a second wheel spaced apart from the first wheel, a first tie rod, a second tie rod, and an electrical actuator. The first wheel is rotatably coupled to a first knuckle, and the first knuckle is pivotable about a first suspension post. The second wheel is rotatably coupled to a second knuckle, and the second knuckle is pivotable about a second suspension post spaced apart from the first suspension post. The first tie rod is coupled to the first knuckle and to a mechanical linkage. The second tie rod is coupled to the second knuckle and the mechanical linkage. The electrical actuator is coupled to the mechanical linkage so that movement of the electrical actuator translates the mechanical linkage axially, which adjusts the orientation of the wheels relative to the suspension posts.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Patent ApplicationSer. No. 62/830,176, filed Apr. 5, 2019, the content of which is herebyincorporated by reference in its entirety.

BACKGROUND

Many lift devices are designed to be mobile. Lift devices are commonlyequipped with a drivetrain incorporated into a base of the lift device.The drivetrain can supply rotatable power to wheels, which in turnrotate to move the lift device. Like the work platform of the liftdevice, the orientation of the wheels is typically controlled using ahydraulic cylinder. The hydraulic cylinder requires the use ofhighly-pressurized hydraulic fluid.

SUMMARY

One exemplary embodiment relates to a steering system. The steeringsystem includes a first wheel, a second wheel spaced apart from thefirst wheel, a first tie rod, a second tie rod, and an electricalactuator. The first wheel is rotatably coupled to a first knuckle, whichis pivotable about a first suspension post. The second wheel isrotatably coupled to a second knuckle that is pivotable about a secondsuspension post. The first tie rod has a first end pivotally coupled tothe first knuckle and a second end pivotally coupled to a mechanicallinkage. The second tie rod has a first end pivotally coupled to thesecond knuckle and a second end pivotally coupled to the mechanicallinkage. The electrical actuator is coupled to the mechanical linkage.Movement of the electrical actuator translates the mechanical linkageaxially. Axial movement of the mechanical linkage pivots the first tierod relative to the first knuckle and pivots the second tie rod relativeto the second knuckle. Pivoting the first tie rod relative to the firstknuckle adjusts an orientation of the first wheel relative to the firstsuspension post. Pivoting the second tie rod relative to the secondknuckle adjusts an orientation of the second wheel relative to thesecond suspension post.

Another exemplary embodiment relates to a lift device. The lift devicehas a base, a retractable lift mechanism, a platform, and a steeringsystem. The base has at least two rotatable and pivotable wheels. Afirst end of the retractable lift mechanism is coupled to the base,while the second end is coupled to and supports the platform. Thesteering system is positioned within an outer perimeter of the base andextends between the two pivotable wheels. The steering system includes afirst knuckle, a second knuckle, a first tie rod, a second tie rod, andan electrical actuator. The first knuckle and the second knuckle areeach coupled to one of the pivotable wheels. The first tie rod has afirst end pivotally coupled to the first knuckle and a second endpivotally coupled to a drag link. The second tie rod has a first endpivotally coupled to the second knuckle and a second end pivotallycoupled to the drag link. The electrical actuator is coupled to the draglink. Movement of the electrical actuator translates the drag linkaxially. Axial movement of the drag link pivots the first tie rodrelative to the first knuckle and pivots the second tie rod relative tothe second knuckle, which adjusts the orientation of the pivotablewheels. The retractable lift mechanism can be a scissor lift or a boomlift, for example.

Another exemplary embodiment relates to a scissor lift. The scissor liftincludes a base, a retractable lift mechanism, a platform, and asteering system. The base has two front wheels and two rear wheels. Theretractable lift mechanism has a first end coupled to the base and has alinear actuator to transition the retractable lift mechanism between astowed position and a deployed position. The platform is coupled to andsupported by a second end of the retractable lift mechanism. Thesteering system extends between the two front wheels, and includes afirst knuckle, a second knuckle, a first tie rod, a second tie rod, andan electrical linear actuator. The first knuckle and second knuckle areeach coupled to one of the front wheels. The first tie rod has a firstend pivotally coupled to the first knuckle and a second end pivotallycoupled to a drag link. The second tie rod has a first end pivotallycoupled to the second knuckle and a second end pivotally coupled to thedrag link. The electrical linear actuator is coupled to the drag link.Movement of the electrical linear actuator along a first axis translatesthe drag link along a second axis parallel to the first axis. Movementof the drag link along the second axis pivots the first tie rod relativeto the first knuckle and pivots the second tie rod relative to thesecond knuckle, which adjusts an orientation of the two front wheelsrelative to the base.

The invention is capable of other embodiments and of being carried outin various ways. Alternative exemplary embodiments relate to otherfeatures and combinations of features as may be recited herein.

BRIEF DESCRIPTION OF THE FIGURES

The disclosure will become more fully understood from the followingdetailed description, taken in conjunction with the accompanyingfigures, wherein like reference numerals refer to like elements, inwhich:

FIG. 1A is a side perspective view of a lift device in the form of ascissor lift, according to an exemplary embodiment;

FIG. 1B is another side perspective view of the scissor lift of FIG. 1A;

FIG. 2 is a rear view of the scissor lift of FIG. 1A, depicting variousvehicle controllers;

FIG. 3 is a bottom perspective view of the steering system of FIG. 1B;

FIG. 4 is a top perspective view of the steering system of FIG. 1B,shown in isolation;

FIG. 5 is a top view of the steering system of FIG. 4 ;

FIG. 6A is a top perspective view of the steering system of FIG. 1B,steering the lift device counterclockwise;

FIG. 6B is a bottom view of the steering system of FIG. 6A;

FIG. 7A is a top perspective view of the steering system of FIG. 1B,steering the vehicle clockwise;

FIG. 7B is a bottom view of the steering system of FIG. 7A;

FIG. 8 is a top, front perspective view of another steering system,according to an exemplary embodiment;

FIG. 9 is a top view of the steering system of FIG. 8 ;

FIG. 10 is a top, rear perspective view of the steering system of FIG. 8;

FIG. 11 is a schematic illustration of another steering system,according to an exemplary embodiment;

FIG. 12 is a schematic illustration of another steering system,according to an exemplary embodiment;

FIG. 13 is a schematic illustration of another steering system,according to an exemplary embodiment;

FIG. 14 is a schematic illustration of another steering system,according to an exemplary embodiment;

FIG. 15 is a top perspective view of another steering system, accordingto an exemplary embodiment; and

FIG. 16 is a side perspective view of another lift device in the form ofa boom lift, according to another exemplary embodiment.

DETAILED DESCRIPTION

Before turning to the figures, which illustrate the exemplaryembodiments in detail, it should be understood that the presentapplication is not limited to the details or methodology set forth inthe description or illustrated in the figures. It should also beunderstood that the terminology is for the purpose of description onlyand should not be regarded as limiting.

Referring to the figures generally, the various exemplary embodimentsdisclosed herein relate to systems, apparatuses, and methods forsteering a lift device, such as a scissor lift or a boom lift. Thesteering systems incorporate an electric linear actuator and drag linkthat are movable along parallel axes to steer the wheels of lift device.The steering systems overcome cross-directional loading limitationsnormally associated with linear actuators by isolating the linearactuator from other components within the steering system duringoperation. Isolating the linear actuator from the remaining componentswithin the steering system prevents the linear actuator fromexperiencing unwanted and potentially damaging non-linear loading. Usingthe steering system of the present disclosure, an electric linearactuator can sufficiently replace the hydraulic cylinder normallypresent within the steering system of the lift device. Removing thehydraulic cylinder at least partially eliminates the need forpressurized hydraulic fluids onboard the lift device, which may besubject to leaking and difficult to service. In embodimentsincorporating an electric lift actuator, leak-prone hydraulic fluids canbe entirely eliminated from the lift device to produce a fully-electriclift device.

Referring now to FIGS. 1A and 1B, a lift device 10 is shown. The liftdevice 10 can take the form of a vehicle that can transport a user and amobile elevating work platform (MEWP) simultaneously. The lift device 10can be a scissor lift or boom lift (e.g., boom lift 810, shown in FIG.16 ), for example, which can be used to perform a variety of differenttasks at various elevations. The lift device 10 includes a base 12supported by wheels 14A, 14B positioned about the base 12. A retractablelift mechanism, shown as a scissor lift mechanism 16, is coupled to thebase 12 and supports a work platform 18. As depicted in FIG. 3 , a firstend 20 of the scissor lift mechanism 16 is anchored to the base 12,while a second end 22 of the scissor lift mechanism 16 supports the workplatform 18.

In some embodiments, the scissor lift mechanism 16 is formed of a seriesof linked, foldable support members 23. The scissor lift mechanism 16 isselectively movable between a retracted, or stowed position and adeployed, or work position using an actuator 24. The actuator 24 can bean electric linear actuator, for example. The actuator 24 controls theorientation of the scissor lifting mechanism 16 by selectively applyingforce to the scissor lifting mechanism 16. When a sufficient force isapplied to the scissor lifting mechanism 16 by the actuator 24, thescissor lifting mechanism 16 unfolds or otherwise deploys from thestowed, rest position. Because the work platform 18 is coupled to thescissor lifting mechanism 16, the work platform 18 is also raised awayfrom the base 12 in response to the deployment of the lifting mechanism16. Although described as being an electric linear actuator, theactuator 24 can also take the form of a hydraulic cylinder (not shown)or a pneumatic cylinder (not shown).

A battery 26 can be positioned onboard the base 12 of the lift device 10to supply electrical power to various operating systems present on thelift device 10. The battery 26 can be a rechargeable lithium-ionbattery, for example, which is capable of supplying a direct current(DC) or alternating current (AC) to lift device 10 controls, motors,actuators (e.g., actuator 24), and the like. The battery 26 can includeat least one input 28 capable of receiving electrical current torecharge the battery 26. In some embodiments, the input 28 is a portcapable of receiving a plug (not shown) in electrical communication withan external power source, like a wall outlet. The battery 26 can beconfigured to receive and store electrical current from one of atraditional 120 V outlet, a 240 V outlet, a 480 V outlet, an electricalpower generator, or another suitable electrical power source. In someembodiments, the battery 26 is in communication with a lift controller27 (shown in FIG. 2 ), which may command the battery 26 to selectivelysupply electrical power to the actuator 24 to control the height and/orposition of the work platform 18 and the scissor lift mechanism 16.

The battery 26 can be in communication with a vehicle controller 29, asshown in FIG. 5 , which selectively controls the supply of electricalpower from the battery 26 to a motor 30 to drive the lift device 10. Themotor 30 can be an AC motor (e.g., synchronous, asynchronous, etc.) or aDC motor (shunt, permanent magnet, series, etc.) for example, whichreceives electrical power from the battery 26 or other electricitysource on board the lift device 10 and converts the electrical powerinto rotational energy in a drive shaft (not shown). The drive shaft canbe used to drive the wheels 14A, 14B of the lift device 10 using atransmission (not shown). The transmission can receive torque from thedrive shaft and subsequently transmit the received torque to a rear axle32 of the lift device 10. Rotating the rear axle 32 also rotates therear wheels 14A on the lift device 10, which propels the lift device 10.

The rear wheels 14A of the lift device 10 can be used to drive the liftdevice 10, while the front wheels 14B can be used to steer the liftdevice 10. In some embodiments, the rear wheels 14A are rigidly coupledto the rear axle 32, and are held in a constant orientation (e.g.,approximately aligned with an outer perimeter 34) relative to the base12 of the lift device 10. In contrast, the front wheels 14B arepivotally coupled to the base 12 of the lift device 10. The front wheels14B can be coupled to vertical suspension posts 36, 38 that are mountedto a front of the base 12. The wheels 14B can be rotated relative to thebase 12 about the vertical suspension posts 36, 38 (e.g., using wheelknuckles 100, 102) to adjust a direction of travel for the lift device10.

The front wheels 14B can be oriented using a steering system 40, asdepicted in additional detail in FIGS. 3-5 . The steering system 40 isan actively adjustable system that operates using a linear actuator 42in lieu of a hydraulic cylinder. The steering system 40 can be mountedto the underside of the base 12 of the lift device 10, for example, andmechanically coupled to each of the two front wheels 14B (e.g., usingfasteners 44). In some embodiments, the steering system 40 is completelycontained within the outer perimeter 34 of the base 12 of the liftdevice 10. As explained in additional detail below, the linear actuator42 can be moved to various different positions to orient the frontwheels 14B of the lift device 10 in a desired direction of lift device10 travel.

The linear actuator 42 includes a piston 46 movable about an axis X-Xusing a motor 48. The motor 48 can be received within a housing 50 thatis coupled to an underside of the base 12 of the lift device 10. Likethe motor 30, the motor 48 within the linear actuator 42 is suppliedwith electrical power from the battery 26. The motor 48 rotates a driveshaft (not shown) contained within the housing 50, which in turn drivesa belt or gear(s). The belt or gear can be used to transmit torque fromthe drive shaft to a lead screw (not shown), which rotates. Rotationalmotion of the lead screw drives a lead screw nut (not shown) coupled tothe piston 46, which translates linearly about the lead screw, along theaxis X-X, as the lead screw rotates. The piston 46 can move into or outof the housing 50.

The linear actuator 42 is coupled to a mechanical linkage that rotatesthe front wheels 14B of the lift device 10. The mechanical linkageincludes a drag link 54 that moves in concert with the piston 46 of thelinear actuator 42. The drag link 54 can be an elongate bar or tube, forexample, that is mounted to the piston 46 using a linkage 56. Thelinkage 56 can be pivotally coupled to the piston 46 and rigidly mountedto the drag link 54. In some embodiments, the linkage 56 is welded tothe drag link 54 and pin-mounted to the piston 46. A pin 58 can extendthrough both the linkage 56 and a distal end 60 of the piston 46 tosecure the linkage 56 to the piston 46.

The allowable motion of the drag link 54 can be governed by the piston46 of the linear actuator 42, along with a bearing housing 62. Thebearing housing 62 can include a mounting flange 64 and sleeve 66extending away from the mounting flange 64. The mounting flange 64includes a flat surface designed to sit flush upon the underside of thebase 12. The mounting sleeve 66 defines a cylindrical passage throughthe bearing housing 62 that can receive the drag link 54. In someembodiments, the cylindrical passage is designed to form a clearance fitwith the drag link 54. The bearing housing 62 can include one or morebearings (not shown) to help promote sliding movement of the drag link54 through the sleeve 66. Alternatively, the mounting sleeve 66 of thebearing housing 62 can include a lubricant (e.g., oil) to help promotesliding motion between the drag link 54 and the mounting sleeve 66. Oneor more seals (not shown) can be positioned between the drag link 54 andthe bearing housing 62 to avoid lubricant leakage. In some embodiments,the drag link 54 and mounting sleeve 66 are arranged so that the draglink 54 translates along a second axis Y-Y, which can be parallel to theaxis X-X. The drag link 54 and mounting sleeve 66 can be approximatelycentered between the front wheels 14B of the lift device 10.

Each end 68, 70 of the drag link 54 can include a mounting tab 72, 74.The mounting tabs 72, 74 can each provide a generally flat surfacesurrounding a through hole 76, 78. The through hole 76, 78 is adapted toreceive a fastener or pin, for example, which can join the drag link 54to additional components. The mounting tabs 72, 74 can be formedintegrally (i.e., continuously) with the drag link 54 or can beotherwise rigidly mounted to the drag link 54. In some embodiments, themounting tabs 72, 74 are welded to each end 68, 70 of the drag link 54.Alternatively, through holes can be formed in the drag link 54 near eachend 68, 70 of the drag link 54 so that mounting tabs 72, 74 can beomitted.

As depicted in FIGS. 3-5 , the mounting tabs 72, 74 of the drag link 54can each support a tie rod 80, 82. A first tie rod 80 is pivotallymounted to the mounting tab 72 on the first end 68 of the drag link 54,while a second tie rod 82 is pivotally mounted to the mounting tab 74 onthe second end 70 of the drag link 54. Pins 84, 86 can be used torotatably mount a first end 88, 90 of one of the tie rods 80, 82 to eachend 68, 70 of the drag link 54. The tie rods 80, 82 can each besuspended below the base 12 of the lift device 10.

The second, opposite end 92, 94 of each tie rod 80, 82 can be coupled toone of the front wheels 14B of the lift device 10. Like the first end88, 90, the second end 92, 94 of the tie rod 80, 82 can also receive apin 96, 98 to couple the tie rods 80, 82 to the front wheels 14B. Thepin coupling securely links the tie rod 80, 82 to the wheel 14B, whileallowing some limited rotatable motion between the front wheel 14B andthe tie rod 80, 82 it is mounted to. In some embodiments, the wheels 14Bare coupled to the tie rods 80, 82 using wheel knuckles 100, 102. Thewheel knuckles 100, 102 each support a front wheel 14B and are rotatablymounted to the base 12 of the lift device 10. The orientation of thewheel knuckles 100, 102 controls the orientation of the front wheels 14Band, consequently, the steering of the lift device 10. The front wheels14B can rotate about the wheel knuckles 100, 102 to move the lift device10.

The tie rods 80, 82 can have an arcuate shape designed to handle tensileloading. For example, each tie rod 80, 82 can be defined by a rigid,arcing member extending angularly between about 135 and 215 degrees. Asdepicted in FIG. 5 , each tie rod 80, 82 is defined by an arc extendingapproximately 180 degrees between the first end 88, 90 and the secondend 92, 94. The arc can be defined by a constant radius or,alternatively, a variable radius. Similarly, the tie rods 80, 82 can bedefined by a uniform thickness throughout, or can vary. For example, thethickness of the tie rods 80, 82 can increase as the distance away fromeach of the ends 88, 90, 92, 94 increases (e.g., a point of maximummaterial thickness occurs near the center of each tie rod 80, 82). Insome embodiments, the tie rods 80, 82 have identical sizes.

The orientation of the front wheels 14B and the steering of the liftdevice 10, more broadly, can be controlled using the steering system 40.As depicted in FIGS. 3-7B, the mechanical linkage formed between thelinear actuator 42, the drag link 54, the tie bars 80, 82, and the wheelknuckles 100, 102 creates an Ackerman geometry steering system 40 thatis controlled by the linear actuator 42. Specifically, the position ofthe piston 46 determines the orientation of the front wheels 14B of thelift device 10. Simultaneously, the pivotable coupling between thepiston 46 and the drag link 54 partially isolates the piston 46 from thedrag link 54 and ensures that only linear forces interact with thepiston 46 of the linear actuator 42. The dual pin nature of the piston46 and the drag link 54 reduces transverse loading of the piston 46.

The linear actuator 42 of the steering system 40 is in electricalcommunication with both the battery 26 and the vehicle controller 29.The vehicle controller 29 is configured to receive and execute steeringcommands. In some embodiments, the linear actuator 42 is hard wired toboth the battery 26 and the vehicle controller 29. When the vehiclecontroller 29 receives a steering command (e.g., a desired steeringorientation from a user through a steering wheel or joystick), thevehicle controller 29 can first determine the current orientation of thefront wheels 14B. The current orientation of the front wheels 14B isdetermined by detecting (e.g., using a sensor or encoder) or otherwiseknowing the current position of the piston 46 of the linear actuator 42.If the desired steering orientation does not match the currentorientation of the front wheels 14B, the vehicle controller 29 can issuea command to the motor 48 of the linear actuator 42 to either retract orfurther advance the piston 46 relative to the housing 50. In some otherembodiments, the steering system 40 and vehicle controller 29 respond toa command from a user (e.g., through a steering wheel or joystick) byadjusting the linear actuator 42 without using or needing current frontwheel 14B orientation information.

If the vehicle controller 29 receives a command to orient the frontwheels 14B further counterclockwise, the motor 48 can activate toretract the piston 46 further into the housing 50. As depicted in FIGS.6A and 6B, the piston 46 is positioned in a fully-retracted position.Because the drag link 54 is coupled to the piston 46, the drag link 54follows the piston 46 laterally, along the second axis Y-Y. The ends 68,70 of the drag link 54 and the tie rods 80, 82 that are coupled to theends 68, 70 of the drag link 54 also move laterally when the drag link54 is adjusted by the piston 46. Because the degrees of freedom in thetie rods 80, 82 are limited by the rotatable couplings on each end 88,90, 92, 94 of the tie rod 80, 82, the wheel knuckles 100, 102 rotatewhen the piston 46 moves.

The rotatable coupling formed between the wheel knuckles 100, 102, thetie rods 80, 82, and the drag link 54 rotates the front wheels 14B inresponse to lateral movement by the drag link 54. As shown in FIG. 5 ,the second end 92, 94 of each tie rod 80, 82 is eccentrically coupled toa wheel knuckle 100, 102, offset from a rotation point 106, 108 for thewheel knuckle 100, 102. The tie rods 80, 82 can be pivotally coupled toa flange 110, 112 of the wheel knuckle 100, 102 that extends forwardfrom the rotation point 106, 108 (when the front wheels 14B are orientedstraight forward). Due to the eccentric mounting of the tie rods 80, 82to the flanges 110, 112, movement of the drag link 54 transmits atensile force within the tie rod 80 and a compressive force within thetie rod 82 that creates a torque on each wheel knuckle 100, 102sufficient to rotate the wheel knuckles 100, 102 about their respectiverotation points 106, 108. Rotation of the wheel knuckle 100, 102 aboutthe rotation points 106, 108 rotates the front wheels 14B about thevertical suspension posts 36, 38, and changes the steering orientationof the lift device 10. Since the rear wheels 14A are fixed in aforward-aligned orientation relative to the base 12 of the lift device10, rotating the front wheels 14B causes the vehicle to turn in thedirection the front wheels 14B are pointed.

If the vehicle controller 29 instead receives a command to orient thefront wheels 14B further clockwise, the motor 48 can activate to advancethe piston 46 further outward from the housing 50. As depicted in FIGS.7A and 7B, the piston 46 is positioned in a fully exposed position. Asindicated above, the drag link 54 is coupled to the piston 46 and moveswith the piston 46 laterally along the second axis Y-Y when the piston46 advances along the axis X-X. The ends 68, 70 of the drag link 54 andthe tie rods 80, 82 that are coupled to the ends 68, 70 of the drag link54 also move laterally when the drag link 54 is adjusted by the piston46.

Once again, the rotatable coupling formed between the wheel knuckles100, 102, the tie rods 80, 82, and the drag link 54 rotates the frontwheels 14B in response to lateral movement by the drag link 54. Theeccentric coupling formed between the second end 92, 94 of each tie rod80, 82 and the wheel knuckles 100, 102 pushes one wheel knuckle 100outward (transmitting a compressive force) and pulls the other wheelknuckle 102 inward (transmitting a tensile force), toward the base 12 ofthe lift device 10. The front wheels 14B turn about the rotation points106, 108 when the wheel knuckles 100, 102 rotate, which changes thesteering of the lift device 10.

Various alternative component arrangements can be incorporated into thesteering system 40 of the lift device 10 according to the disclosure.For example, the drag link 54 can be positioned in front of the linearactuator 42, rather than behind. Different arc lengths and shapes can beused for each tie rod 80, 82 as well. In some embodiments, the tie rods80, 82 are linear components. In still other embodiments, the steeringsystem 40 can be incorporated into the rear wheels 14A of the liftdevice 10, rather than the front wheels. Rather than a scissor lift, thelift device 10 can be an articulated boom, a telescopic boom, or othertype of MEWP. The steering system 40 is compatible with and can beincorporated into nearly any type of electric vehicle. In still otherembodiments, the linear actuator 42 can be replaced with a hydrauliccylinder.

Referring now to FIGS. 8-10 , another exemplary embodiment of a steeringsystem, shown as steering system 240, is depicted. Like the steeringsystem 40, the steering system 240 is configured to orient the frontwheels 14B of the lift device 10. In some embodiments, the steeringsystem 240 may be used in place of the steering system 40, describedabove. The following description will focus mainly on the differencesbetween the steering system 240 and the steering system 40. However, itwill be appreciated that various aspects of the steering system 40and/or the steering system 240 may be interchangeable. That is, in someembodiments, various aspects of the steering system 40 may beimplemented into the steering system 240, and vice versa.

As illustrated, the steering system 240 similarly includes a linearactuator 242 including a piston 246 that is axially movable using amotor 248. The motor 248 functions similarly to the motor 48, and issimilarly supplied with power from the battery 26 to selectively movethe piston 246 into and out of a housing 250. The linear actuator 242 issimilarly coupled to a drag link 254 that moves in concert with thepiston 246. The piston 246 is similarly pivotally coupled to a linkage256, which is rigidly coupled to the drag link 254, thereby effectivelycoupling the piston 246 to the drag link 254.

The allowable motion of the drag link 254 can be governed by the piston246 of the linear actuator 242 along with a roller housing 276. Theroller housing 276 includes a guide component 278 and a roller component280. The guide component 278 is rigidly coupled to the roller component280 using various connection links 282 and fasteners 284. The guidecomponent 278 includes a guide channel 286 (shown in FIG. 8 ) configuredto slidably receive the drag link 254. In some embodiments, the guidechannel 286 may have interior bearings (not shown) to help promotesliding motion of the drag link 254 through the guide channel 286. Insome other embodiments, the guide channel 286 may include a lubricant(e.g., oil) to help promote the sliding motion of the drag link 254through the guide channel 286.

The roller component 280 includes a pair of rollers 288 disposed atopposite axial ends of the roller component 280. The pair of rollers 288are configured to engage a lateral side of the drag link 254, oppositethe guide channel 286. In some embodiments, the pair of rollers 288comprise a high-strength plastic material. For example, the pair ofrollers 288 may comprise ultra-high-molecular-weight polyethylene(UHMW). The pair of rollers 288 can comprise various other materials aswell, which can be selected based the intended application. The pair ofrollers 288 may be configured to act as both a stabilizer for the draglink 254 during use, and also as a shock absorber to further isolate thepiston 246 from transverse forces.

As such, the drag link 254 is slidably received within the rollerhousing 276, between the guide component 278 and the roller component280, and is configured to slide axially within the roller housing 276.Each end 290, 292 of the drag link 254 similarly supports and ispivotally coupled to a corresponding one of the tie rods 80, 82.Accordingly, the orientation of the front wheels 14B and the steering ofthe lift device 10, more broadly, can be controlled using the steeringsystem 240 in a near identical manner to that described above, withreference to the steering system 40.

In addition to the pair of rollers 288, various components of thesteering system 240 may comprise a high-strength plastic material. Forexample, in some embodiments, similar to the pair of rollers 288,various components of the steering system 240 may comprise UHMW. In someother embodiments, various components of the steering system 240 maycomprise metallic materials.

Referring now to FIG. 11 , another exemplary embodiment of a steeringsystem, shown as steering system 340, is depicted. Like the steeringsystems 40, 240, the steering system 340 is configured to orient thefront wheels 14B of the lift device 10. In some embodiments, thesteering system 340 may be used in place of the steering systems 40, 240described above. The following description will focus mainly on thedifferences between the steering system 340 and the steering systems 40,240.

The steering system 340 similarly includes a linear actuator 342configured to selectively actuate a piston 346. The piston 346 issimilarly pivotally coupled to a linkage 356, which is rigidly coupledto a drag link 354. The drag link 354 is slidably received within a pairof linear bearings 376. The linear bearings 376 are configured to allowthe drag link 354 to slide axially, in a direction substantiallyparallel to the axial direction of the piston 346. Each end 390, 392 maybe similarly pivotally coupled to a corresponding one of the tie rods80, 82. As such, the orientation of the front wheels 14B and thesteering of the lift device 10, more broadly, can be controlled usingthe steering system 340 in a near identical manner to that describedabove, with reference to the steering systems 40, 240. Again, thepivotal coupling between the piston 346 and the linkage 356 may allowfor the piston 346 to be at least partially isolated from undesirabletransverse loading.

Referring now to FIG. 12 , another exemplary embodiment of a steeringsystem, shown as steering system 440, is depicted. Like the steeringsystems 40, 240, 340, the steering system 440 is configured to orientthe front wheels 14B of the lift device 10. In some embodiments, thesteering system 440 may be used in place of the steering systems 40,240, 340 described above. The following description will focus mainly onthe difference between the steering system 440 and the steering systems40, 240, 340 described above.

The steering system 440 includes a rotational pinion gear 476, which maybe selectively rotated using an electric motor (not shown) similar tomotor 48. The rotational pinion gear 476 is engaged with a drag link 454and configured to selectively actuate the drag link 454 axially.Specifically, teeth (not shown) of the pinion gear 476 are configured toengage teeth (not shown) on the drag link 454 to provide an axial forceon the drag link 454. Linear bearings 478, which may be rigidly fixed tothe bottom of the lift device 10, slidably receive the drag link 454 andare configured to retain the drag link 454 in a desired axialorientation. Each end 490, 492 may be similarly pivotally coupled to acorresponding one of the tie rods 80, 82. As such, the orientation ofthe front wheels 14B and the steering of the lift device 10, morebroadly, can be controlled using the steering system 440 in a similarmanner to that described above, with reference to the steering systems40, 240, 340. The automotive-style rack-and-pinion type actuation of thesteering system 440 used to swivel the front wheels 14B allows for themotor and pinion gear 476 to be compactly arranged at the center of thelift device 10.

Referring now to FIG. 13 , another exemplary embodiment of a steeringsystem, shown as steering system 540, is depicted. Like steering systems40, 240, 340, 440, the steering system 540 is configured to orient thefront wheels 14B of the lift device 10. In some embodiments, thesteering system 540 may be used in place of the steering systems 40,240, 340, 440 described above. The following description will focusmainly on the difference between the steering system 540 and thesteering systems 40, 240, 340, 440 described above.

The steering system 540 may be a chain or belt based steering system.Specifically, the steering system 540 includes a driving gear set 542, achain or timing belt 544, a pair of sprockets or pulleys 546, a linkage548, a drag link 554, and a plurality of bearings 556. The driving gearset 542 may be selectively rotated using an electric motor, similar tothe motor 48. The driving gear set 542 is configured to engage andprovide an axial force on the chain or timing belt 544. The pair ofsprockets or pulleys 546 are configured to engage the chain or timingbelt 544, which is wrapped around the sprockets or pulleys 546 to form achain/timing belt loop. Ends 558 of the chain or timing belt 544 arerigidly coupled to the linkage 548. As such, actuation of the drivinggear set 542 is configured to selectively move the linkage 548 axially.

The linkage 548 is rigidly fixed to the drag link 554, which is held ina constant axial orientation by the plurality of bearings 556. Theplurality of bearings 556 are configured to slidable receive the draglink 554, such that the drag link 554 may be selectively actuated by thelinkage 548. Accordingly, selective actuation of the driving gear set542 is configured to selectively actuate the linkage 548, and therebythe drag link 554. Each end 590, 592 may be similarly pivotally coupledto the a corresponding one of the tie rods 80, 82. As such, theorientation of the front wheels 14B and the steering of the lift device10, more broadly, can be controlled using the steering system 540 in asimilar manner to that described above, with reference to the steeringsystems 40, 240, 340, 440. Once again, the configuration of the steeringsystem 540 allows for the motor and drive gear set 542 to be arranged atthe center of the lift device 10. Further, the belt-type actuation ofthe steering system 540 effectively isolates the motor from anytransverse shock loads.

Referring now to FIG. 14 , another exemplary embodiment of a steeringsystem, shown as steering system 640, is depicted. Like steering systems40, 240, 340, 440, 540, the steering system 640 is configured to orientthe front wheels 14B of the lift device 10. In some embodiments, thesteering system 640 may be used in place of the steering systems 40,240, 340, 440, 540 described above. The following description will focusmainly on the difference between the steering system 640 and thesteering systems 40, 240, 340, 440, 540 described above.

The steering system 640 includes a pair of linear actuators 642. Each ofthe linear actuators 642 may be structured substantially similar to thelinear actuator 42 described above. The linear actuators 642 eachinclude an axially-movable piston 646. A distal end of each of thepistons 646 is pivotally coupled to a corresponding tie rod 680, 682.The tie rods 680, 682 of the steering system 640 may be substantiallysimilar to the tie rods 80, 82 described above. An opposite end of eachtie rod 680, 682 may be pivotally coupled to a corresponding flange 684,686. The flanges 684, 686 may be coupled to and configured to controlthe orientation of the front wheels 14B. As such, the steering system640 effectively includes two independent steering subsystems 688 thatmay be collectively used to control the orientation of the orientationof the front wheels 14B and the lift device 10, more broadly. Theindependent nature of the steering subsystems 688 allows for the linearactuators 642 to be mounted in differing orientations on the bottom ofthe lift device 10. Further, the independent nature of the steeringsubsystems 688 may allow for a more flexible steering capability.Additionally, the pivotal connections between the linear actuators 642and the tie rods 680, 682 in conjunction with the pivotal connectionsbetween the tie rods 680, 682 and the flanges 684, 686 may eliminatelateral forces exerted onto the piston 646. Further still, the directmounting of the linear actuators 642 and the tie rods 680, 682 may allowfor the linear actuators 642 to be run at a lower actuator speed.

Referring now to FIG. 15 , yet another exemplary embodiment of asteering system, shown as steering system 740, is depicted. Like thesteering systems 40, 240, 340, 440, 540, 640, the steering system 740 isconfigured to orient replacement front wheels 14B of the lift device 10.In some embodiments, the steering system 740 may be used in place of thesteering systems 40, 240, 340, 440, 540, 640 described above. Thefollowing description will focus mainly on the difference between thesteering system 740 and the steering systems 40, 240, 340, 440, 540, 640described above.

The steering system 740 includes a wheel orientation motor 742 coupledto a rotatable wheel flange 744. The wheel orientation motor 742 ismountable onto the bottom of the base 12, and is configured toselectively rotate the rotatable wheel flange 744. The rotatable wheelflange 744 is configured to be rotatably coupled to a corresponding oneof the front wheels 14B. In use, the lift device 10 may have acorresponding steering system 740 for each of the front wheels 14B (orthe rear wheels 14A) to selectively orient the lift device 10 whiledriving.

It will be appreciated that various aspects of the steering systems 40,240, 340, 440, 540, 640, 740 described above may be interchangeable.That is, in some embodiments, various aspects of the steering systems40, 240, 340, 440, 540, 640, 740 may be implemented into any of theother steering systems 40, 240, 340, 440, 540, 640, 740.

Additionally, while the retractable lift mechanism included on liftdevice 10 is a scissor lift mechanism, in some instances, a vehicle maybe provided that alternatively includes a retractable lift mechanism inthe form of a boom lift mechanism. For example, in the exemplaryembodiment depicted in FIG. 16 , a vehicle, shown as vehicle 810, isillustrated. The vehicle 810 includes a retractable lift mechanism,shown as boom lift mechanism 816. The boom lift mechanism 816 issimilarly formed of a series of linked, foldable support members 823.The boom lift mechanism 816 is selectively movable between a retractedor stowed position and a deployed or work position using a plurality ofactuators 824. Each of the plurality of actuators 824 may be an electricactuator.

Advantageously, vehicles 10, 810 may be fully-electric lift devices. Allof the electric actuators and electric motors of vehicles 10, 810 can beconfigured to perform their respective operations without requiring anyhydraulic systems, hydraulic reservoir tanks, hydraulic fluids, enginesystems, etc. That is, both vehicles 10, 810 may be completely devoid ofany hydraulic systems and/or hydraulic fluids generally. Saiddifferently, both vehicles 10, 810 may be devoid of any moving fluids.Traditional lift devices do not use a fully-electric system and requireregular maintenance to ensure that the various hydraulic systems areoperating properly. The vehicles 10, 810 may use electric motors andelectric actuators, which allows for the absence of combustible fuels(e.g., gasoline, diesel) and/or hydraulic fluids. As such, the vehicles10, 810 may be powered by batteries, such as battery 26, that can bere-charged when necessary.

Although this description may discuss a specific order of method steps,the order of the steps may differ from what is outlined. Also two ormore steps may be performed concurrently or with partial concurrence.Such variation will depend on the software and hardware systems chosenand on designer choice. All such variations are within the scope of thedisclosure. Likewise, software implementations could be accomplishedwith standard programming techniques with rule-based logic and otherlogic to accomplish the various connection steps, processing steps,comparison steps, and decision steps.

As utilized herein, the terms “approximately”, “about”, “substantially”,and similar terms are intended to have a broad meaning in harmony withthe common and accepted usage by those of ordinary skill in the art towhich the subject matter of this disclosure pertains. It should beunderstood by those of skill in the art who review this disclosure thatthese terms are intended to allow a description of certain featuresdescribed and claimed without restricting the scope of these features tothe precise numerical ranges provided. Accordingly, these terms shouldbe interpreted as indicating that insubstantial or inconsequentialmodifications or alterations of the subject matter described and claimedare considered to be within the scope of the invention as recited in theappended claims.

It should be noted that the term “exemplary” as used herein to describevarious embodiments is intended to indicate that such embodiments arepossible examples, representations, and/or illustrations of possibleembodiments (and such term is not intended to connote that suchembodiments are necessarily extraordinary or superlative examples).

The terms “coupled,” “connected,” and the like, as used herein, mean thejoining of two members directly or indirectly to one another. Suchjoining may be stationary (e.g., permanent, etc.) or moveable (e.g.,removable, releasable, etc.). Such joining may be achieved with the twomembers or the two members and any additional intermediate members beingintegrally formed as a single unitary body with one another or with thetwo members or the two members and any additional intermediate membersbeing attached to one another.

References herein to the positions of elements (e.g., “top,” “bottom,”“above,” “below,” “between,” etc.) are merely used to describe theorientation of various elements in the figures. It should be noted thatthe orientation of various elements may differ according to otherexemplary embodiments, and that such variations are intended to beencompassed by the present disclosure.

It is important to note that the construction and arrangement of thesteering system as shown in the exemplary embodiments is illustrativeonly. Although only a few embodiments of the present disclosure havebeen described in detail, those skilled in the art who review thisdisclosure will readily appreciate that many modifications are possible(e.g., variations in sizes, dimensions, structures, shapes andproportions of the various elements, values of parameters, mountingarrangements, use of materials, colors, orientations, etc.) withoutmaterially departing from the novel teachings and advantages of thesubject matter recited. For example, elements shown as integrally formedmay be constructed of multiple parts or elements. It should be notedthat the elements and/or assemblies of the components described hereinmay be constructed from any of a wide variety of materials that providesufficient strength or durability, in any of a wide variety of colors,textures, and combinations. Accordingly, all such modifications areintended to be included within the scope of the present inventions.Other substitutions, modifications, changes, and omissions may be madein the design, operating conditions, and arrangement of the preferredand other exemplary embodiments without departing from scope of thepresent disclosure or from the spirit of the appended claims.

What is claimed is:
 1. A steering system, comprising: a first wheel anda second wheel laterally spaced apart from the first wheel; a thirdwheel and a fourth wheel laterally spaced apart from the third wheel,wherein the third wheel and the fourth wheel are both longitudinallyspaced from the first wheel and the second wheel, and wherein the thirdwheel and the fourth wheel are both pivotally fixed in a forward-alignedorientation, the first wheel and the second wheel defining a traveldirection, the first wheel rotatably coupled to a first knuckle, thefirst knuckle being pivotable about a first suspension post and thesecond wheel being rotatably coupled to a second knuckle, the secondknuckle being pivotable about a second suspension post spaced apart fromthe first suspension post; a first tie rod having a first end pivotallycoupled to the first knuckle and a second end pivotally coupled to adrag link; a second tie rod having a first end pivotally coupled to thesecond knuckle and a second end pivotally coupled to the drag link; andan electrical actuator coupled to the drag link, wherein the drag linkis arranged in front of the electrical actuator relative to the traveldirection; wherein movement of the electrical actuator translates thedrag link axially, and wherein axial movement of the drag link pivotsthe first tie rod relative to the first knuckle and pivots the secondtie rod relative to the second knuckle, wherein pivoting the first tierod relative to the first knuckle adjusts an orientation of the firstwheel relative to the first suspension post and wherein pivoting thesecond tie rod relative to the second knuckle adjusts an orientation ofthe second wheel relative to the second suspension post.
 2. The steeringsystem of claim 1, wherein the drag link is defined by a first end and asecond end opposite the first end, the first end of the drag linksupporting a first pin coupling securing the first tie rod to the draglink, the second end of the drag link supporting a second pin couplingsecuring the second tie rod to the drag link.
 3. The steering system ofclaim 2, wherein the electrical actuator is a linear actuator having ahousing and a motor-driven piston movable relative to the housing, themotor-driven piston being movable about a first axis.
 4. The steeringsystem of claim 3, wherein the electrical actuator is pivotally coupledto the drag link, the drag link being configured to move, in response tomovement of the motor-driven piston relative to the housing, about asecond axis offset from the first axis.
 5. The steering system of claim4, wherein the first axis and the second axis extend parallel to oneanother.
 6. The steering system of claim 4, wherein the drag link isslidably received within a roller housing, the roller housing includingat least one roller contacting the drag link to guide the drag linkalong the second axis.
 7. The steering system of claim 1, wherein thefirst tie rod is coupled to a first flange formed on the first knuckle,the first flange extending away from the first suspension post such thataxial motion of the drag link imparts a torque onto the first flangethat rotates the first knuckle and first wheel about the firstsuspension post.
 8. The steering system of claim 7, wherein the firsttie rod and the second tie rod are each defined by an arcuate shape. 9.The steering system of claim 1, wherein axial movement of the drag linkin response to movement by the electrical actuator in a first directiontransmits a tensile force through the first tie rod and transmits acompressive force through the second tie rod, the tensile force causingthe first knuckle to rotate about the first suspension post in a firstrotational direction and the compressive force causing the secondknuckle to rotate about the second suspension post in the firstrotational direction.
 10. The steering system of claim 9, wherein axialmovement of the drag link in response to movement by the electricalactuator in a second direction transmits a compressive force through thefirst tie rod and transmits a tensile force through the second tie rod,the compressive force associated with movement in the second directioncausing the first knuckle to rotate about the first suspension post in asecond rotational direction opposite the first rotational direction andthe tensile force causing the second knuckle to rotate about the secondsuspension post in the second rotational direction.
 11. The steeringsystem of claim 1, wherein the drag link is defined by a first end and asecond end opposite the first end, the first end of the drag linksupporting a first pin coupling securing the first tie rod to the draglink, the second end of the drag link supporting a second pin couplingsecuring the second tie rod to the drag link, and wherein the drag linkis slidably received within linear bearings.
 12. The steering system ofclaim 1, wherein the drag link is defined by a first end and a secondend opposite the first end, the first end of the drag link supporting afirst pin coupling securing the first tie rod to the drag link, thesecond end of the drag link supporting a second pin coupling securingthe second tie rod to the drag link, wherein the electrical actuator isa motor supplying rotational power to a pinion gear having a firstplurality of gear teeth, and wherein the drag link includes a secondplurality of gear teeth meshed with the first plurality of gear teethsuch that rotation of the pinion gear caused by the motor translates thedrag link axially.
 13. The steering system of claim 1, wherein the draglink is defined by a first end and a second end opposite the first end,the first end of the drag link supporting a first pin coupling securingthe first tie rod to the drag link, the second end of the drag linksupporting a second pin coupling securing the second tie rod to the draglink, wherein the electrical actuator is a motor supplying rotationalpower to a belt, the belt being coupled to a linkage that extends awayfrom the drag link and translates the drag link axially in a firstdirection in response to clockwise belt rotation and translates the draglink axially in a second direction opposite the first direction inresponse to counterclockwise belt rotation.
 14. A lift devicecomprising: a base having at least two rotatable and pivotable wheelsand two pivotally fixed wheels held in a constant forward-alignedorientation, the two pivotal wheels defining a travel direction; aretractable lift mechanism having a first end coupled to the base; aplatform coupled to and supported by a second end of the retractablelift mechanism; and a steering system positioned within an outerperimeter of the base and extending between the two pivotable wheels,the steering system comprising: a first knuckle and a second knuckleeach coupled to one of the pivotable wheels; a first tie rod having afirst end pivotally coupled to the first knuckle and a second endpivotally coupled to a drag link; a second tie rod having a first endpivotally coupled to the second knuckle and a second end pivotallycoupled to the drag link; and an electrical actuator coupled to the draglink, wherein the drag link is arranged in front of the electricalactuator relative to the travel direction; wherein movement of theelectrical actuator translates the drag link axially, and wherein axialmovement of the drag link pivots the first tie rod relative to the firstknuckle and pivots the second tie rod relative to the second knuckle,wherein pivoting the first tie rod relative to the first knuckle andpivoting the second tie rod relative to the second knuckle adjusts anorientation of the two pivotable wheels.
 15. The lift device of claim14, wherein the lift device is a scissor lift, and wherein theelectrical actuator is a linear actuator, the linear actuator includinga piston movable relative to a housing, and wherein the piston iscoupled to the drag link so that movement of piston relative to thehousing about a first axis translates the drag link about a second axisoffset from and parallel to the first axis.
 16. The lift device of claim15, wherein the drag link is slidably received within a roller housing,the roller housing being mounted to the base and including at least oneroller contacting the drag link to guide the drag link along the secondaxis.
 17. The lift device of claim 14, wherein the lift device is a boomlift, and wherein the electrical actuator is a linear actuator, thelinear actuator including a piston movable relative to a housing, andwherein the piston is coupled to the drag link so that movement ofpiston relative to the housing about a first axis translates the draglink about a second axis offset from and parallel to the first axis. 18.The lift device of claim 14, further comprising a controller incommunication with the electrical actuator, the controller beingconfigured to issue a command to adjust an operational parameter of theelectrical actuator in response to receiving a steering command.
 19. Ascissor lift comprising: a base having two front wheels and two rearwheels, the two front wheels defining a travel direction, the two rearwheels being pivotally fixed in a forward-aligned orientation; aretractable lift mechanism having a first end coupled to the base andhaving a linear actuator to transition the retractable lift mechanismbetween a stowed position and a deployed position; a platform coupled toand supported by a second end of the retractable lift mechanism; and asteering system extending between the two front wheels, the steeringsystem comprising: a first knuckle and a second knuckle each coupled toone of the front wheels; a first tie rod having a first end pivotallycoupled to the first knuckle and a second end pivotally coupled to adrag link; a second tie rod having a first end pivotally coupled to thesecond knuckle and a second end pivotally coupled to the drag link; andan electrical linear actuator coupled to the drag link, wherein the draglink is arranged in front of the electrical actuator relative to thetravel direction; wherein movement of the electrical linear actuatoralong a first axis translates the drag link along a second axis parallelto the first axis, and wherein movement of the drag link along thesecond axis pivots the first tie rod relative to the first knuckle andpivots the second tie rod relative to the second knuckle, and whereinpivoting the first tie rod relative to the first knuckle and pivotingthe second tie rod relative to the second knuckle adjusts an orientationof the two front wheels relative to the base.
 20. The scissor lift ofclaim 19, wherein the drag link is slidably received within a guide thatis mounted to the base, the guide being one of a roller housing, abearing housing, and a linear bearing.